Tag Archives: Sea Hare

Invertebrate Locomotion in the Ocean

At the Catalina Island Marine Institute, we are all about being active and on the move.  The same goes for the invertebrates in our labs! But how do they move? Magic? Super powers? Thinking happy thoughts? Actually, we can explain with…..science!

Some of the animals in our lab move by using their little tube feet.  These are animals like the sea stars, sea cucumbers, and urchins, which are all members of the phylum Echinodermata.  Echinodermata translates to “spiny skin”.  Not only do the members of this phylum have spines, they also have sticky little feet! In fact, if you look underneath any of these animals, you will see what looks like little tubes with suction cups on the ends.  The animal will extend these tube  feet in the direction it wants to go, suction on, and then pull itself along.  Sometimes the tube feet can also be used as levers and for food capture. The tube feet can also be used to help the animal stay in place, if say, kids—I mean… “seagulls”—..were trying to grab at them! So cool.

Some of the friends in our Mollusk tank, such as the California Sea Hare, Aplysia californica, and the Spanish Shawl nudibranch, Flabellina iodinea, move in a different way.  These animals have a soft slug-like body, the length of which is called a “foot”.  Weird, I know, imagine if your whole body was called a foot! So the foot produces slime and when the animal contracts its muscles and moves tiny hairs on its body through the slime it manages to scoot, scoot, scoot! 

As if this wasn’t enough, many of the slugs can also swim (Fig.2)  The Spanish Shawl and the Lion’s Mane, Melibe leonina, can swim by whipping their head back and forth towards the end of  their foot. It can be an effective way to respond to predators, and kind of looks like they are throwing down for a dance off.

The take away here is that there are many ways to move through life, and invertebrates are great role models for showing us how it’s done! There’s no right or wrong way, whether you have many sticky feet, a whole body called a foot to scoot around on slime with, or maybe you just whip back and forth—- no kind of motion is too “loco” to be in the ocean!

https://www.britannica.com/animal/echinoderm

http://www.divedownbelow.com/marine-biology/nudibranchia-marine-biology/

http://pacificabeachcoalition.org/sea-stars/tube-feet-of-spiny-starfish-borut-furlan-getty/

Mucus in the Animal Kingdom

Boogers. There. I said it. Now you are all thinking about thoseooey gooey slimy’s that drip from our noses when we are sick. But our bodies produce mucus every day—it helps protect our lungs by capturing dust and dirt when we inhale. Mucus production ins’t only a human process, however. Lots of different animals produce mucus for a variety of different reasons. Take these Catalina ocean dwellers, for instance:

California Sheephead

Mucus sheephead

At night this fish may produce a mucus cocoon around its body. This inhibits predators from using their sense of smell to find these fish while they are resting.

For more on this species: https://www.montereybayaquarium.org/animal-guide/fishes/california-sheephead

Sea Hare

mucus sea hare

As a defense the sea hare can produce a purple ink and something called opaline. This slimy, sticky secretion was studied a few years ago. It is believed to interfere with a predator’s ability to taste and smell.

For more on this species: https://blogs.scientificamerican.com/running-ponies/sea-hares-thwart-spiny-lobster-attack-with-goo/

Pacific Hagfish

mucus

The slimiest of them all. Pacific hagfish create slime as a defense against predators. Their slippery bodies allow them to flee from the mouths of predators and slip into tiny crevices.

For more on this species: https://news.nationalgeographic.com/2017/03/hagfish-oceans-slime-deep-weird/

 

The Invertebrate: Sea Hare

The sea hare is one of the most amazing invertebrates you can see in the waters surrounding Catalina Island and here at CIMI. You can find two different species in our coves and our aquariums – the California sea hare and the black sea hare. Sea hares belong to the phylum mollusca, making them relatives of other gastropods like slugs and snails, as well as squids, octopuses, and clams. These marvelous molluscs were named sea hares (Latin: lepus marinus) by the ancient Romans because of their rhinophores, two appendages on the top of the animal’s head that look a lot like rabbit ears. Sea hares also display large wing-like flaps on their backs known as parapoidea, which can sometimes be used for swimming. The California sea hare can grow to be as large as sixteen inches long and five pounds, while the black sea hare is the largest gastropod, sometimes reaching over two feet long and more than thirty pounds!

Sea Hare 1The sea hare begins its life as one of as many as eighty million eggs, all laid in a large mass that looks a little bit like a bunch of spaghetti. Only twelve days after being laid, the sea hare larvae are ready to hatch. For the first thirty days of its life, a larval sea hare is planktonic. This means that the animal is largely unable to control its movements and floats about on ocean waves and currents. After about thirty days, the sea hare has grown large enough to no longer be planktonic. Over the next three months, the sea hare will double its body weight every ten days! Scientists who study sea hares have found that small juvenile individuals seem to prefer deeper water (up to 60 feet), while adults seem to prefer shallower water. But no matter how deep they live, sea hares will always prefer rocky areas with lots of algae for them to munch on. They especially love red algae, which gives them their dark red to brown (and black) coloring. In the California sea hare, the red algae also make the animals’ ink a purpleish-red color. The California sea hare uses this irritating ink as a defense mechanism against predators. Around Catalina, you can find sea hares enjoying a red algae snack of plocamium or pterocladia.

Sea Hare 3

A California sea hare’s bright red ink – thanks to algae!

After about four months, sea hares reach maturity and are capable of laying eggs of their own. All species are hermaphroditic. This means that each individual is capable of acting as both a male and a female during reproduction. As many as twenty individuals can gather at the same time in order to reproduce in what scientists call mating chains.

The typical lifespan for a sea hare is only about one year, however, cooler water like that surrounding Catalina Island helps to extend the lifespan by delaying the spawning (mating) process.

Insided Look: California Sea Hare

Don’t get confused by the name, California sea hares are actually a type of sea slug commonly found in intertidal zones along the coast of California and Mexico. Their color depends on the food they eat. One of their favorite foods is the red algae plocamium, which is what gives many of them a pinkish-red color, but others can appear more brown. This helps the sea hare blend into their environment, and they will usually spend most of their time hiding in intertidal seaweed. Sea hares accumulate toxins from the algae they eat and store them in their body, making them distasteful to most predators. When attacked, California sea hares will expel a bright purple ink, which is mildly toxic to some animals.

Though sea hares like to live in shallower waters, they cannot move around outside of the water like other intertidal creatures. Their soft bodies are supported by a hydrostatic skeleton, which is a system of fluid-filled cavities surrounded by muscle. When the sea hare moves, it changes shape by flexing these muscles and pushing the fluid in different directions. This only works because the pressure of the fluid inside the sea hare’s body is equal to the pressure of the water outside it. Outside of water, this system breaks down, and the sea hare turns into a shapeless, immobile lump.

Sea hares have been compared to rabbits since ancient times because of the ear-like structures on top of their heads. These are actually chemical receptors called rhinophores, which the sea hare uses to detect dissolved chemicals in the water. This helps it locate food and track down the pheromone secretions of other sea hares. Sea hares are hermaphrodites, which means they possess both male and female parts. Once one or more potential mates are found, they will sometimes form daisy chains, which is a line of slugs all mating at once.

It is hard not to fall in love with the sea hare. Their squishy bodies and bunny-like appearance make them very charismatic representatives of the amazing creatures we can find in the intertidal zone. Next time you go tidepooling, take a peak in the seaweed and see if you can find one of these camouflaged algae-lovers. Just make sure you keep that hydrostatic skeleton intact and leave it in its watery home.

DCIM104GOPROGOPR1774.

Hello Bunny…I mean Sea Hare!

Written by: Megan Petkovic

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